SYNTHESIS AND CHARACTERIZATION OF POLYNUCLEAR COMPLEXES OF MOLYBDENUMCARBONYL DERIVATIVES WITH PYRIDINE-2-CARBALDEHYDE AZINE (PA) AND FERROCENYLPHOSPHINES - CRYSTAL-STRUCTURE OF [MO-2(CO)(6)(MU-DPPF)(MU-PA)] (DPPF = 1,1'-BIS(DIPHENYLPHOSPHINO)FERROCENE)

Novel mono- and didentate ferrocenylphosphines containing complexes, [ Mo-2(CO)(6)(dfpp)(2)(mu-pa)] (dfpp = diferrocenylphenylphosphine) and [Mo-2(CO)(6)(mu-dppf)(mu-pa)], have been isolated and characterized by infrared and electronic spectroscopy, and cyclic voltammetry. For the [Mo-2(CO)(6)(mu-dppf)(mu-pa)] complex a single crystal X-ray structur e analysis evidences its double bridge nature and the asymmetry of the bridging ligands due to steric constraints. In the visible region, th e new compounds show strong solvatochromic bands and this effect has b een evaluated by using the E-MLCT parameter. The redox behaviour of t he complexes involves molybdenum and ferrocene-based oxidations and pa -based reductions. The results are compared to the previously characte rized analogous complexes based on the related ligands triphenylphosph ine and 1,2-bis(diphenylphosphino)ethane. (C) 1998 Elsevier Science Lt d. All rights reserved.